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Ploidy Number

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Ploidy Number

Postby Tokophyra125 » Mon Mar 03, 2008 2:43 am

For some reason "calculating" the diploid and haploid number of an organism/cell is messing me up. If I have a cell with four pairs of homologous chromosomes, the diploid number should be four, right? Also, if there is an organism with a haploid number of X then what would the number for a bivalent, sister chromatid, and a nucleus after DNA replication be?
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Postby Tokophyra125 » Mon Mar 03, 2008 2:50 am

Sorry, rather a diploid number of 4.
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Postby biogeek02 » Fri Mar 07, 2008 5:36 pm

Check out http://www.bioinmotion.com for cool vids about meiosis and mitosis!
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Re: Ploidy Number

Postby Cat » Fri Mar 07, 2008 6:22 pm

Tokophyra125 wrote:For some reason "calculating" the diploid and haploid number of an organism/cell is messing me up. If I have a cell with four pairs of homologous chromosomes, the diploid number should be four, right? Also, if there is an organism with a haploid number of X then what would the number for a bivalent, sister chromatid, and a nucleus after DNA replication be?


The whole thing is wrong.

Vocabulary:

Haploid – half of total number of chromosomes
Mono– one
Di – Two
Tetra – four
Octa – eight

Cell that has only 1 set of chromosomes (no sister chromatids) is monoploid. Monoploid is sometimes treated as synonym of haploid when haploid number happens to be 1.

Cell that has 2 of each chromosome (like humans) are diploid.

Cells from your example, that have four pairs of homologous chromosomes in reality have 8 copies of each chromosome and, therefore, octaploid.

Haploid cell will have half of chromosomes in original somatic cell. So if original is diploid (2n), haploid is 1n; if original is octaploid (8 of each chromosome), haploid has 4 sets of each chromosome.
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